📌 Quick Answer
The SI unit of electrical conductivity is siemens per metre (S/m), also written as Ω−1·m−1 (mho per metre).
Conductivity (σ) is the reciprocal of resistivity: σ = 1 / ρ.
🔹 Key Takeaways
- SI unit of electrical conductivity = siemens per metre (S/m).
- Conductivity is the reciprocal of resistivity: σ = 1/ρ.
- 1 siemens (S) = 1 ohm−1 (mho).
- Thermal conductivity has a different unit: W/m·K.
What Is Conductivity?
Electrical conductivity (σ) measures how easily a material allows electric current to flow through it. A high conductivity means current flows easily (good conductor); a low value means it resists current (insulator).
SI Unit of Conductivity
The SI unit of electrical conductivity is siemens per metre (S/m). Since 1 siemens = 1 ohm−1, it can also be written as Ω−1m−1 or mho/m.
Relation Between Conductivity and Resistivity
σ = 1 / ρ
Conductivity is the reciprocal of resistivity (ρ), whose SI unit is the ohm-metre (Ω·m). So as resistivity falls, conductivity rises.
Conductivity vs Conductance
| Quantity | Symbol | SI unit |
|---|---|---|
| Conductivity | σ | S/m |
| Conductance | G | siemens (S) |
| Molar conductivity | Λm | S·m²/mol |
Note: Thermal Conductivity Has a Different Unit
Do not confuse electrical conductivity (S/m) with thermal conductivity, which measures heat conduction and has the SI unit watt per metre kelvin (W/m·K).
Frequently Asked Questions
What is the SI unit of conductivity?
The SI unit of electrical conductivity is siemens per metre (S/m), equivalent to Ω⁻¹·m⁻¹.
What is the formula for conductivity?
Conductivity is the reciprocal of resistivity: σ = 1/ρ.
What is the unit of molar conductivity?
The SI unit of molar conductivity is S·m²/mol.
What is the SI unit of thermal conductivity?
Thermal conductivity has the SI unit watt per metre kelvin (W/m·K), which is different from electrical conductivity.